gradle: driver is now set by BndPlugin

Signed-off-by: BJ Hargrave <bj@bjhargrave.com>
Use new Workspace.setDriver method to set bnd driver

This is instead of directly setting the -bnd-driver workspace property.

Signed-off-by: BJ Hargrave <bj@bjhargrave.com>
Merge pull request #876 from bjhargrave/setdriver

Use new driver API in Workspace to set the driver to "eclipse"